Kids who grow up on traditional farms are 30 percent to 50 percent less likely than other children to develop asthma, a new study shows. But it's not the fresh country air. It's the germs.

"Good" germs, that is, or at least harmless ones associated with cows, pigs and other barnyard creatures with which humans have been living, and maybe even co-evolving, for centuries.

Farm children whose household dust has the greatest variety of bacteria and fungi are much less likely to develop asthma and allergies than non-farmers, whose homes had fewer microscopic inhabitants, says the study of 933 European children in today's New England Journal of Medicine.

The study could help doctors better understand why childhood asthma rates have doubled in the past 30 years, says James Gern of the University of Wisconsin School of Medicine and Public Health, who was not involved in the study. About one in 10 U.S. children have asthma, according to the federal Centers for Disease Control and Prevention in Atlanta.

Though certain germs and microbes can make us sick, our bodies depend on others to function, says lead author Markus Ege of Munich University Children's Hospital in Germany.

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Microbial cells make up about 90 percent of the cells in our bodies and help us perform basic tasks such as digesting food, Ege says.

But scientists can't explain precisely how farm germs protect against disease.

Read the rest of this article at USAToday.com PD

—Source: USAToday.com